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Symmetry between up and down quarks is more broken than expected

(phys.org)
87 points terminalbraid | 5 comments | 29 Mar 25 10:12 UTC | HN request time: 1.094s | source
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ptsneves ◴[31 Mar 25 15:17 UTC] No.43536027[source]▶
What are the consequences for this breakage? The article says current models do not easily fit the asymmetry but does not state what parts of our understanding will break if those models are wrong.
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fpoling ◴[31 Mar 25 15:31 UTC] No.43536209[source]▶
Strong interactions are notoriously difficult to calculate from the first principles. So typically it is not done, but rather theoreticians try to guess the result and use the experimental data to partially fill the calculation gaps.

So I expect in this cases the guesses were wrong and the Standard Model will manage to explain that as well.

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staunton ◴[31 Mar 25 17:01 UTC] No.43537213[source]▶
Working like that, it sounds like the standard model can explain literally anything...
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exe34 ◴[31 Mar 25 17:10 UTC] No.43537294[source]▶
the standard model isn't one thing, it's the sum total of human knowledge of particle physics. it's an equation with a gazillion terms - this is an adjustment to one of those terms. and yes, you can add terms for any new physics you discover, so technically you're right, but it's not a gotcha.
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1. yummypaint ◴[31 Mar 25 17:27 UTC] No.43537490[source]▶
This makes it sound more ad hoc than it is, it's not some polynomial where people just tack on terms.

In its current agreed upon form it's just SU(3)xSU(2)xU(1). This gauge symmetry defines the lagrangian, which has 19 parameters to be determined by experiment.

It's true that this isn't the whole story (dark matter etc), but these symmetries are physically motivated and their predictive power is pretty amazing (the QED part is CORRECT as far as any experiment has been able to check so far).

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2. exe34 ◴[31 Mar 25 19:46 UTC] No.43539036[source]▶
thank you! one day I'll understand this stuff - I skipped the qft elective at uni, but I'm trying to learn more now.
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3. eru ◴[01 Apr 25 01:33 UTC] No.43541933[source]▶
'The standard model' also doesn't include gravity. And we do have pretty good theories about gravity.

So it's definitely not the 'sum total of human knowledge'.

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4. exe34 ◴[01 Apr 25 08:08 UTC] No.43544077{3}[source]▶
Does particle physics include gravity now?
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5. eru ◴[01 Apr 25 09:20 UTC] No.43544584{4}[source]▶
Sorry, I missed that.

But yes in a sense: we do know that particles are subject to gravity. So that is part of 'the sum total of human knowledge of particle physics.'